I noticed the Mpts totals had suddenly become large and negative, and one of the optimisations had a best result of 80%. There were some results from luigi (BOINC wrapper) that had negative Mpts values and one had the huge muon percentage. Probably an unstable machine. I've removed the results I could see and modified the stats machine results filter to reject negative-Mpts results (oddly it only rejected zero-Mpts results up to now).